It is a process in which a metal is deposited on another metal electrolytically.
🎯 Three main objectives of electroplating
1. Decoration: To deposit noble metals like gold and silver on inexpensive metals to enhance their beauty.
2. Protection: To protect metals from rusting as well as from the reaction of organic acids.
3. Repair: To weld the broken parts of machinery by electrodeposition of metals. Generally copper, silver, chromium, nickel and gold are electroplated.
💡 Noble metals: Gold, silver and platinum are chemically unreactive and valuable – called noble metals.
🛠️ Procedure of Electroplating
The article to be electroplated is first cleaned with sand and then washed with caustic soda solution and finally with plenty of water. This article is then made a cathode, while the metal to be deposited is made anode. The electrolyte is a salt of the metal being deposited and the electroplating is carried out in a tank made of cement, glass or wood. It is called an electrolytic tank.
✅ Electrolyte must have:
very soluble in water
good conductor
not easily oxidized or reduced or hydrolyzed
inexpensive
⚡ Conditions for good deposits:
High current density
Low temperature
Higher concentration of the metal in its electrolyte
The procedure for silver plating is the same except that the electrolyte used is the solution of potassium argento cyanide, K[Ag(CN)₂], and anode is of pure silver. The following ions are formed in the electrolytic solution.
When electric current is passed, Ag⁺ ions migrate towards the cathode and deposit after picking up electrons. Cyanide ions move towards the anode, where they react with silver to form AgCN, which combines with KCN to reproduce the electrolyte, K[Ag(CN)₂].
In copper plating, the anode is made of copper metal and the electrolyte is CuSO₄ to which a few drops of sulphuric acid are added to prevent its hydrolysis. The article to be electroplated is made the cathode. The following electrolytic reactions take place:
At Anode: Cu(s) → Cu²⁺(aq) + 2e⁻ At Cathode: Cu²⁺(aq) + 2e⁻ → Cu(s)
Interesting Information: Chromium plating is usually done on iron or steel. As chromium does not directly adhere to iron properly, iron is first copper or nickel plated.
⚡ 16.7 Quick Check! (solved)
1. What is the principle behind electroplating?
✅ Answer: Electroplating is based on the electrolytic deposition of metal ions onto a cathode. The metal to be deposited is made anode and dissolves, while ions in the electrolyte get reduced and plate the article (cathode).
2. How electroplating is used to repair worn-out areas of metal objects?
✅ Answer: By making the worn-out object the cathode in an electrolytic bath containing ions of the same metal. Metal is deposited onto the worn areas, building up thickness and restoring the shape (electroforming / repair plating).
Lesson planner (45 min)
5 min – Show plated objects (jewellery, taps), ask how they are made.
10 min – Explain objectives (decoration, protection, repair) and basic setup.
10 min – Silver & copper plating reactions (board work).
7 min – Solve 16.7 Quick Check together.
8 min – Hands-on activity (simulate plating with nail and copper sulfate).
5 min – MCQ quiz (first 5 questions) & summary.
Activities for students
🧪 Copper plating experiment: Use copper sulfate solution, iron nail (cathode), copper strip (anode), 6V battery. Observe pink copper deposit on nail after 5 minutes.
💍 Design a “gold” coin: Research how gold plating is done. Write three steps.
🔎 Compare: Silver plating vs copper plating – differences in electrolyte and uses.
🎨 Poster: “How chromium plating is done on steel” (include nickel undercoat).
📘 Student success guidelines – Electroplating
Remember: Cathode = object to be plated (reduction: Mⁿ⁺ + n e⁻ → M). Anode = pure metal (oxidation: M → Mⁿ⁺ + n e⁻).
Electrolyte must contain ions of the plating metal – often complexed (like cyanide for silver) to get smooth deposit.
For good finish: high current density, low temp, high metal ion concentration.
Chromium needs an undercoat of copper or nickel for adhesion.
📝 10 MCQs Quiz (electroplating, silver, copper)
Click option – correct turns green, others red. Submit to see score & key.